I can only write on my own experience, a 06 plate 1.9jtdm that I have owned since it was 1 year old (i.e. I have had it almost 6 years now).
Here is what has gone wrong with it in those 6 years:
1 - from new, it had a very annoying buzzing noise from the rear quarter. After several trips to the garege we tracked it down to a loose velvet wheel arch lining, easily fixed once found.
2 - a year in I got the very common "wrong colour steering rack fluid" - caused the power steering to creak and groan at low speeds. Soon fixed by a new resevoir and correct colour steering fluid.
3 - not an error, but I had my engine remapped and dpf removed 3 years in - better performance and fuel economy. despite being an alfa owner, its the better fuel economy I really wanted.
4 - got a few false alarms when it was windy, dealer put it right
5 - front passenger door lock failed, had to have it replaced
6 - front outside drivers mirror came loose from the fixing plate, repaired it myself with double sided sticky tape
7 - no failure, but when I had my 60,000 mile major service, the independent dealer recommended I have my water pump changed at the same time he changed the cam belt. Turned out to be a good thing as he showed me the old water pump which was not far off failure.
8 - my glow plug warning light comes on, but the engine starts without hesitation. My local mechanic told me not to worry about it 6 months ago, and it has started up without hesitation all winter.
That's it. Might look like a long list, but nothing catostrophic, mostly routine work. Despite the extra power from the remap, I am on 70k miles and had no clutch problems. I had a 3 series bmw before this, a company car which I owned from new, and it had far more problems including failed steering on the second day of ownership.
From personal experience, I would not hesitate to buy another Alfa now. But that is based on just one car.